An example of prior art automatic door opening and closing systems is shown in Unexamined Japanese Patent Publication (KOKAI) No. HEI 2-208584. The system disclosed in this unexamined Japanese patent publication has one object detector including an ultrasonic Doppler sensor having a single sectorial door enabling area around it. When the detector senses an object, such as a human, approaching an automatic door, it generates a signal, which is used to arithmetically determine the distance of the object from the detector as well as its moving speed. When the calculated distance of the object becomes equal to the distance of the edge of the door enabling area from the detector, i.e. when the moving object reaches the edge of the door enabling area, the system accounts the object to be moving toward the automatic door. If the speed of the object when it is at the edge of the enabling area is high, the automatic door is opened when the object passes a predetermined point within the enabling area relatively remote from the door. If the object's speed determined at the edge of the enabling area is low, the automatic door is opened when the object reaches a point within the enabling area nearer to the door.
In this type of automatic door opening system, the location within the enabling area which is reached by the moving object to thereby cause the automatic door open is determined in accordance with the speed of the object at the edge of the enabling area. However, the speed of the object moving in the enabling area is not always the same as the speed of the object at the edge of the enabling area. If, for example, the object moving slowly at the edge of the enabling area moves faster after it enters the enabling area, it may occur that the door has not been opened, while the moving object has reached the front of the door. On the other hand, if the object moving fast at the edge of the enabling area slows down after it enters the enabling area, the door may be opened before the object has reached the door, so that it will take a longer time for the moving object to have passed through the door into a room after the door is opened. This means that the door is opened for a longer time, which can disadvantageously make air-conditioning of the room less effective.
There are various types of doors. One type includes a plurality of panels which are all opened or closed by a single driving system. One example of this type is a four-panel sliding door (or sometime called four sliding doors). When a moving object approaches any one of the four panels of the door, all of the four panels are pulled to open the door. However, it is not always necessary to open all of the panels, but it may sometimes be sufficient to open only one or more of the four panels enough to allow the moving object to pass. If all of the panels are unnecessarily opened, the air-conditioning efficiency of the room is disadvantageously lowered.
The object of the present invention is to eliminate the above-described defects of prior art automatic door opening and closing system.
According to the present invention, a monitoring area is provided outside a door enabling area, and the velocity of a moving object approaching a door is measured in the monitoring area. The measured velocity is used to predict the time when the object arrives at the door. The door is energized so that it is fully opened at the predicted arrival time of the object.
According to the present invention, a door enabling area is set inside the monitoring area. The enabling area is set in accordance with the velocity of the moving object within the monitoring area. When the object arrives at the enabling area, the energization of the automatic door is started so that the door is fully opened upon the arrival of the object at the door.
According to another embodiment of the invention, an automatic door includes a plurality of door panels. The panel which the moving object will arrive at is predicted on the basis of the direction of movement of the object, and only the predicted panel is driven to open.
According to another aspect of the invention, a monitoring area is set around the panels of the plural-panel automatic door, and the direction of movement of the object is determined within the monitoring area to predict which the panel the object will arrive at. A door enabling area is set in the vicinity of the predicted panel, and upon the arrival of the object at the outer edge of the enabling area, the panel is started to be driven so that it is fully opened upon the arrival of the object at the panel.